The development of a natural gas-fired combustor for direct-air heaters

The Institute of Gas Technology (IGT) and Maxon Corporation, with gas industry funding support, are developing a gas-fired, air-cooled cyclonic combustor for relatively low-temperature direct-air heating applications that require particulate-free, ultra-low pollutant emissions. High-lean premixed combustion with flame stabilization is used to achieve ultra-low emissions and high turndown operation. Based on analytical studies and cold modeling, a 735-kWth test combustor was designed and successfully tested. Experimental results with ambient air demonstrated that the combustor can operate steadily at up to 80% excess air and up to 20:1 turndown. At design operating conditions, No[sub x] emission of 1.0 vppm, with CO and total hydrocarbon (THC) emissions each below 3 vppm,* were achieved. This paper presents the concept of high-lean premixed air-cooled ultra-low emission particulate-free cyclonic combustion, design specifications for the combustion system, and the major experimental results, including flame stability, emissions, and turndown performance.